As a communication system including a transmission device, a communication medium, and a reception device, communication technology using a human body as a communication medium is specifically called BAN (Body Area Network), HBC (Human Body Communication), IBC (Intra-body Communication), human body communication, quasi-electrostatic field communication, etc. (which are hereinafter referred to as BAN or human body communication). In the BAN, a user holds a transmission device including a human body-side transmission electrode and a space-side transmission electrode. In this case, the user holds the transmission device so that the human body-side transmission electrode is in closer proximity to a human body than the space-side transmission electrode. The reception device includes a human body-side reception electrode and a space-side reception electrode. The human body-side reception electrode receives a signal through a communication path using a human body as a communication medium with the human body-side transmission electrode, and the space-side reception electrode receives a signal through a communication path using space as a communication medium. In the BAN, it is possible to perform communication only by the user touching the reception electrode. The BAN is expected to be used, for example, in a security field in which unlocking of a door, and the like are performed.